Spinal Cord Stimulation and Functional MRI

The main objective is to define, using functional magnetic resonance imaging, the effects of
spinal cord stimulation (SCS) on cortical and subcortical BOLD effects in patients with
neuropathic leg pain. Our hypothesis is that SCS will demonstrate a consistent pattern of
BOLD activation that will correlate with symptomatic improvement.

Inclusion Criteria:

- Age 18-55 years at time of enrollment.

- Have previous implantation of thoracic epidural Medtronic Restore Ultra, Prime
Advanced and Restore Advanced SCS in place for the treatment of CPRS-type 1 or
chronic refractory neuropathic leg pain following FBSS. The implantation must be 3 or
more months prior to enrollment.

- Patient must have reported significant pain improvement (>50%) following implantation
of the SCS.

- Have consistently reproducible pain relief (> 50%) within 10 minutes of switching SCS
from an OFF state to an ON state (with "optimal" parameters - see below).

- The SCS battery is implanted in the buttocks region.

- Unilateral or bilateral extremity pain.

- Able to provide informed consent.

Exclusion Criteria:

- Contraindication to MRI such as: SCS lead in the cervical epidural region Cardiac
pacemaker Intracranial aneurysm clips, metallic implants or external clips within 10mm of
the head Metallic foreign metals within the orbits Pregnancy; (urine pregnancy test will
be done to confirm) Claustrophobia

- Pattern of response to spinal cord stimulation Inconsistent response of pain to
spinal cord stimulation Long interval (> 10 minutes) before pain relief following
switching SCS from an OFF state to an ON state (with "optimal" parameters) - long
"washout" period Lack of significant pain improvement (< 50%) following implantation
of SCS

- Positive history of significant brain lesions or pathology including:

- Prior ablative neurosurgery

- History of large vessel strokes or brain tumors

- Psychological Screening